1. Field of the Invention
The present invention relates to the production of high dielectric constant thin films, and is particularly directed to a thin film having a high dielectric constant and high dielectric strength for use as a dielectric material in a capacitor or the like.
2. Description of the Prior Art
The thin film composed of tantalum oxide (Ta.sub.2 O.sub.5) and formed by chemical vapor deposition by the oxygen-assisted thermal decomposition of tantalum ethylate (Ta(OC.sub.2 H.sub.5) has a relative dielectric constant of about 25 to 28 which is higher than that of a thin film made of SiO.sub.2, Si.sub.3 N.sub.4, or the like and advantageously may be employed for miniaturizing a capacitive element and for improving the degree of integration of an integrated circuit. For comparison, the relative dielectric constant of SiO.sub.2 is about 3.7 and that of Si.sub.3 N.sub.4 is about 7.
As methods for forming a thin film of Ta.sub.2 O.sub.5, are included a sputtering method, a chemical vapor deposition method, and an anodic oxidation method for Ta film. Of these methods, the chemical vapor deposition method is superior to other methods in its adaptability to mass production.
Although the Ta.sub.2 O.sub.5 thin film can be mass produced by the chemical vapor deposition method as described above, if the film thickness of the Ta.sub.2 O.sub.5 film is less than 500 .ANG., a dimension which is commonly used in practice, the insulating property is poor, that is, its dielectric strength is low. Thus, a Ta.sub.2 O.sub.5 thin film having very low film thicknesses cannot presently be used in practice.
When a Ta.sub.2 O.sub.5 thin film formed by chemical vapor deposition is used as a capacitive element, noble metals such as gold and platinum and the like can be used as the electrodes on both surfaces of this film, and high insulating properties and high dielectric strengths can be obtained. On the other hand, if metals and semiconductors such as aluminum, chromium, silicon and the like are used as electrodes, there arises the problem that the insulating property is deteriorated.